“This new one-hour standard is designed to protect the air we breathe and reduce health threats for millions of Americans. For the first time ever, we are working to prevent short-term exposures in high risk NO2 zones like urban communities and areas near roadways,” EPA Administrator Lisa P. Jackson said in a written statement. “Improving air quality is a top priority for this EPA. We’re moving into the clean, sustainable economy of the 21st century, defined by expanded innovation, stronger pollution standards and healthier communities.”

The agency set the new one-hour standard for NO2 at a level of 100 parts per billion (ppb). EPA also is retaining the existing annual average standard of 53 ppb. NO2 is formed from vehicle, power plant and other industrial emissions, and contributes to the formation of fine particle pollution and smog. Earlier this month, EPA proposed to tighten the nation’s smog standards to protect the health of all Americans, especially children.

EPA is establishing new monitoring requirements in urban areas that will measure NO2 levels around major roads and across the community. Monitors must be located near roadways in cities with at least 500,000 residents. Larger cities and areas with major roadways will have additional monitors. Community-wide monitoring will continue in cities with at least 1 million residents.

EPA says it expects to identify or designate areas not meeting the new standard, based on the existing community-wide monitoring network by January 2012. New monitors must begin operating no later than January 1, 2013.

When three years of air quality data are available from the new monitoring network, EPA intends to redesignate areas as appropriate.